I have just bought a Creative HS-1200 (X-FI) and I want to hear something with OSSv4 under Gentoo Linux (~amd64).I have installed oss-devel from the overlay.soundon run correctly, drivers seems to exists (in beta), but I have no sound.

Well, recently I too came to buy a Creative HS 1200. I too was wondering what it would be like hearing some music with OSSv4 in the Gentoo Linux. Just like you, it was only from overlay that I had installed the OSS devel. However, there seems to be no sound no matter what I try.